I find that one of my credit cards often has problems with the magnetic strip. It's also the one I use the most. Other cards get x-rayed/metal detected just as often and have no problem. So I'm not sure it's the airport security that's killing your card.
If your magnetic strip starts to die, there are a couple of tricks that I've learned from various merchants. First, where possible slide the card in the opposite direction. Second, put a thin strip of scotch tape on the strip.
I have no idea why these two tricks work, but I'm sure some engineer could chime in. For all I know, it's just pacebo effect.
cnk